1. Field of the Invention
The present invention relates generally to devices for assisting the hearing impaired. More particularly, the present invention relates to a bone conduction hearing aid having a vibrator which is placed in the ear.
2. Background of the Invention
Transcranial cross amplification has been used for patients that have a profound sensorineural (permanent) hearing loss in one ear and normal hearing or a mild hearing loss in the other ear. A typical remedial approach used by practitioners has been to employ powerful acoustic speakers which produce an amplified sound so intense to the bad ear that the sound is transferred through bone conduction in the skull to the cochlea of the good ear. The purpose of this approach is to increase hearing sensitivity when the primary signal is coming from the side of the bad ear and also to improve a patient""s signal to noise ratio for speech, especially in situations where noise is being introduced to the good ear. Unfortunately, the acoustic speakers provide a poor transfer of sound when used in a transcranial application (i.e., when the amplified sound output by the speakers is to be used to stimulate the bony portion of the ear canal for transfer through the skull to the good cochlea). Because of the power required, feedback often occurs before an optimal intensity level can be achieved for stimulating the bony portion of the ear canal. Thus, the gain of the instrument must be reduced, which in turn reduces the effectiveness of the hearing aid.
Another remedial approach used by practitioners has been to employ a body type hearing aid with a bone vibrator. Such bone vibrators are normally worn on the mastoid bone behind the ear and are generally used for individuals with conductive losses (outer or middle ear pathology). The bone vibrator used with body hearing aids are typically held in place with a head band that provides a sufficient force to maintain good contact with the mastoid bone. Disadvantages of such hearing aids are that they are aesthetically undesirable and physically uncomfortable.
Therefore, there is a need for an improved bone conduction hearing aid. The hearing aid may be used to improve hearing in ears with conductive pathology.
The present invention eliminates the difficulties and disadvantages of the prior art by providing a hearing aid that enhances a user""s hearing perception. The hearing aid includes an acoustic vibration sensor for sensing acoustic vibrations and producing an acoustic vibration signal corresponding to the sensed acoustic vibrations. The acoustic vibration signal is amplified by electronics to produce an amplified acoustic vibration signal. A power source supplies electrical power to the electronics. A vibrator is positioned in the user""s, or patient""s ear canal adjacent the mastoid bone. The vibrator receives the amplified acoustic vibration signal and produces vibrations which are transmitted to the mastoid bone. Vibrations transmitted to the mastoid bone are transferred transcranial to the opposite cochlea to enhance the user""s hearing perception. Vibrations transmitted to the mastoid bone may also be transferred to the cochlea of an ear with conductive loss to enhance the user""s hearing perception.
Vibration produced by the vibrator may result in undesired feedback to the acoustic vibration sensor. To eliminate such feedback, a feedback reduction circuit is included with the electronics. A user interface may be provided to enable user control of feedback circuit parameters. In an alternate form of feedback reduction/elimination, the acoustic vibration sensor is vibrationally isolated from the vibrator so that vibration produced by the vibrator is not sensed by the acoustic vibration sensor. For example, a vibration attenuating material separates the vibrator and acoustic vibration sensor.
The present invention also provides a method for improving hearing perception in a patient. In accordance with a preferred method, acoustic vibrations are sensed and a corresponding acoustic vibration signal is produced. The acoustic vibration signal is amplified to produce an amplified acoustic vibration signal. A vibrator is positioned in the patient""s ear canal adjacent the mastoid bone. The vibrator is then vibrated with the amplified acoustic vibration signal.